Electrodynamic sound recorder and reproducer



Nov. 11, 1930. B. E. ElsENHoUR 17,781,376

ELECTRODYNAMIC SOUND RECORDER AND REPRODUGER Filed Sept. 24, 1928 nnnnnn n.

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Patented Nov. 11', 1930` UNITED; STATES PATENT ori-Ica BERT EISENHOUR, OF AURORA., ILLINOIS, ASSIG-NOR, BY MESNE ASSIGNMENTS, T0 UNITED REPRODUCERS CORPORATION, OF ST. CHARLES, ILLINOIS, A. CORPORATION OF NEW JERSEY ELECTRODYNAMIC SOUND RECORDER AND EEPRODUCER Application le'd. September 24, 1928. Serial No. 307,949.

The present invention relates to soundv recorders and reproducers, and particularly to those of the electro-dynamic type.

,Among theiobjects of the'invention is to provide a novel electrical device capable of converting mechanical movements and energies into electrical effects and vice versa for sound recording and sound reproduction, the device operating as a motor when recording and asa generator when reproducing.

In a preferred embodiment, the device comprises balanced conductors movable in plural gaps for multiplied energy conversion. Y The coils preferably move in opposite directions,

such that as one coil is moving into a stronger part of the field, the other coil moves into a weaker part of the eld with a resultant compensation and average constant current. The output follows more nearly a sine curve.

Another object of the invention is to pro-4 vide for small movements ofthe coils, such that, as for example, where two coils are used with half the leverage of a single coil having twice the movement, the shorter movements are much closer to a linear movement in cutting the magnetic lines than would be thecase ofthe larger movement of a single coil designed for the same energy conversion. The lateral componentpf movement of two coils having but a small arc movement, as for example a few degrees, 4will be negligible or practically nil. Yet, if'a single coil be given twicethe leverage to get the same energy conversion, twice the arc movement at least, isI

required, but the lateral component movement will be very much more thantwice that in the case of half the angular. movement which is necessary for the two coils of half the leverage. The use of multiple coils, connected in series, with fractional leverage produces a much more eiiicient energy conversion approaching more close-ly to perfect sine curves. This reduces practically all liability of mechanical resonance of parts. Other ad 'vantages are also gained, such as making for a more rigid and stronger structure, a more compact device; less inertia of mas's or mo mentum to overcome, and the like.

Other objects, capabilities advantages and features are comprehended by the invention as will later appear and as are inherently possessed thereby.

Referring to the drawings:

Fig. l is a sectional view taken in a lane represented by line 1--1 in Fig. 2 of the rawings.

Fig. 2 is a sectional view taken in a plane represented by line 2-2 in Fig. 1 of the drawlngs. l

Fig. 3 is a sectional view taken in a plane represented by line 3 3 in Fig. 1 of the drawin s.

ig. 4 is a plan view of the lever used in an illustrative embodiment of the invention, and

Fig. 5 is a detail sectional view, enlarged, of a part of the device.

Referring now more in detail to the drawings, the embodiment selected to illustrate the invention is shown in connection with housing l having a back plate 2 Vwith which is rigidly connected a connector 3 adapted in any suitable manner for connection with a goose-neck of a tone arm of a phonograph or the like, so that it may act as an electrical reproducer or pick-up device, although it is to be .understood that this is merely illusp invention, the magnet 4 is supported by a non-magnetic'plate 6 having a flange 7 by which it is-secured to the back 2 of the housing, as by soldering or by screws 8 threaded into an insulating block 9, or both, as desired. The plate 6 has apertures through which the endsof the ma et 4 protrude to provide poles 10 and 11. ecured to the underside of plate 6, as by securing elements 6a, is a magnetic cross piece 12 having annular pole shoes or pieces 13 and 14 at its ends, the/shoes surroundin the poles 10 and 11 and having apertures o a size to provide annular magnetic gaps 1'5 and 16 between said shoes and the poles 10 and 11.

carrying pivot screws 21 and 22 adapted Y to rotatably support a pivot shaft 22%l tov which is secured a lever 23 having two oppositely extending short arms 24 and 25, andv a depending arm 26 acting as a carrier -for a stylus 27 of either the recording or reproducing type. The lever 23 is of open structure and made of light weight metal such as aluminum. It has side pieces17 and 18 acting as stays or strengthening elements'. The stylus may be heldsecured in the socket of the arm 26 by a thumb screw 28 or the like. A record or matrix 29 is shown in association with the stylus.

At the ends ofthe arms24 and 25 are provided annular parts or rings 30 and 31 with which are connected tubular elements 20 32 and 33 of thin-insulating material, these tubes being very light in weight and serving as spools for windings or coils 34 and 35 of very fine wire. These coils are located in the air or magnetic gaps -15 and 16, and co'axial with the poles 10 and 11 and the shoes 13 and 14, and are also preferably connected in series by a wire 36 passing through suitable apertures provided in the rings 30 and 31 and i in arm 26. The other ends of the coils 34 and 35 have leads 37 and 38 running' to binding screws 39 and 40 secured to the insulatingb block 9 and also acting to bind conducting elements 41 and 42 connected to binding screws 43 and 44 also secured to the insulat- .ing block 9. From the latter binding screws 43 and 44 may run suitable leads to an electrical amplifying device, such as power ampliiers used in radio sets or the like, when l:the device is used as a reproducer or pick-up attachment, or the leads may run toan electrical apparatus for converting sound 'vibrations into 'electrical energy,'in which case the device acts as a recorder for producing sound.

such position when it has been moved, suit-- able resilient or similar members 45 land 46,

such as `Yfelt, rubber or like pads,l are interposed between the upper parts of the arms 24 and 25 and the lower face of the magnetic member 12, as clearly shown in Fig. 1 of the drawings.

In operation the magnet 4 and cross piece 12 with shoes13 and 14`form a magnetic circuit for magnetic iux, the .latter forming a flux field or magnetic lines in the gaps 15 and 16, these lines being substantially at right angles to the axes of the poles 10 and 11. Thelever 23 vibrates about the axis of pivot 22@ to cause the coils 34 and 35 tomove in the gaps 15 and 16 with the convolutions ofv thecoils transversely of the lines of force of the magnetic field in the gaps, this cutting such lines. Inasmuch as the lever arms 24 and 25 are short, themoveixients ofl the coils 34 and-35 inthe gaps 15 and 16 'are prac-I tically lineal and co-axial with thev axes of the poles 10 and 11.

In the case ofthe stylus operating in 'I groove of a record 29, the mechanical vibrations of the stylus are imparted in the lever 23 for moving the coils in the gaps and the cutting of the lines of force causes a consonantvariationin the circuit of the coils and the' amplifying device, the device of this invention acting,'in such case, as an-electrical sound reproducer. When this device is to operate as a recorder, the electrical energy the lever 23 and engraving stylus 27 for producing a sound groove in a matrix 29.

It will' be noted that by using a pair or balanced coils at the ends of a rst class lever, one coil will be moving in an opposite direction to the other., such that as a coil is moving into a strong field the other will be moving into a weak field, so that the resultant effect is an average constantiforce, whether mechanical or electrical depending upon the direction of conversion from electrical to mechanical or from mechanical to electrical 1. A dynamic recorder and reproducer,

comprising magnets having gaps, generating conductors iii said gaps, said conductors being spaced and having axes, 'a vibratile member carrying said conductors for vibration of the conductors transversely to the' magnetic flux in said gaps and along said axes, and means for vibratably supporting said member.

2. A dynamic recorder and reproducer, comprising magnets having gaps, generating conductors in said gaps, a vibratile member carrying saidlconductors for vibration of the conductors in-opposite directions and transversely to the magnetic flux in saidvgaps, and means between said conductors for vibratably supportin g said member.

3.. A dynamic recorder and reproducer,

comprising magnetic elements having magnetic gaps, an elongated supporting member,

generatin conductorscarried at the ends of said mem r andlocated in said gaps, said conductors being spaced and having dierent lao axes, means intermediate the ends of'said member for oscillatably supporting said member whereby said conductors move in said gaps along said axes and across the flux lines therein. l c

4; A dynamic recorder and reproducer, comprising magnetic elements having magf netic gaps, an elongated supporting member, generating conductors carried at the ends of said member and located in said gaps, fulcrum means at an intermediate part of said member for oscillatably supporting said member, and a stylus associated with said member.

5. An electrical recorder and reproducer, comprising magnetic poles having air gaps, coils in said gaps, a support for the coils, and means for oscillatably supporting the support whereby the coils may move in said gaps, and a stylus associated with said support.

6. An electrical recorder and reproducer, comprising magnetic poles having air gaps, coils in said gaps, a support for'the coils, and means for oscillatablysupportingthesupport whereby the coils may move in said gaps, and a stylus associated with'said support, the center of oscillation being located between said coils whereby the coils oscillate in opposite directions.

7. An electrical recorder and reproducer, comprising spaced magnetic gap means, coils adapted to move in the gaps of said means .transversely to the magnetic liux in said gaps, 4

a supporting member for said coils, means for oscillatably supporting said supporting member whereby said coils move in opposite directions, and a stylus associated with the supporting member.

8. A d comprising magnetic members arranged in a magnetic circuit and being provided with a pair `of spaced magnetic gaps, a lever fulcrumed between said gaps and having arms extending to said gaps, generating coils in vsaid gaps and carried by said arms, 'a stylus Yassociated with said lever and adapted to vibrate withsaid lever to cause said coils to vibrate in said gaps across the flux therein and in opposite directions.

9. A dynamic recorder and reproducer,

` comprisin a Ymagnet having spaced poles, a

pole shoe or each pole and spacedtherefrom to provideanannulargapbetween the shoe and the pole, a lever fulcrumed between said poles Y and having short arms extending to said gaps, coils carried at the opposite ends of said' leverand located in said ps, and 4a stylus connected to said lever an vibratable therewith for moving the coils in said gaps in axial directions and with opposite movements for an average constant currentconversion in the coils.

10. A dynamic recorder and reproducer,

BERT E. EISENHOUR.

ynamic recorder and reprodncer, 

